With Manchester United's two major summer purchases - Luke Shaw and Ander Herrera - having been completed prior to the official start of Louis van Gaal's tenure as full-time manager, the Dutch maestro is yet to make his first signing.

In pre-season, Manchester United have experimented - successfully - with a 3-5-2 formation, however, Collymore does not feel that the centre back trident of Chris Smalling, Jonny Evans and Phil Jones is strong enough at the elite-level.

In the recent World Cup tournament in Brazil, the 25-year-old played six times and made 16 tackles, 29 clearances and 11 interceptions whilst also returning an 88% passing accuracy from 289 pass attempts.

Hummels has three years remaining on his BvB contract but is reportedly available for £20 million.